Download Module 1: The Brain and the Central Nervous System (CNS

Module 1: The Brain and the Central Nervous System (CNS)
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Overview of the brain and CNS – how they control everything we do
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Basic anatomy of the brain and nervous system
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Basic “how the brain works” – oxygen and glucose provided by blood
Learning outcomes
At the end of this module, the learner will be able to:
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Understand the relationship between brain and behavior
Explain the basic biology of the brain
Outline the role of the frontal, parietal, temporal and occipital lobes
Describe how the brain is protected from damage
What is Neurology?
Neurology is the field of medicine concerned with the study of the brain, nervous
system, and the neurons. Neurological disorders are therefore conditions which
result from damage to the brain, the spinal cord, or nerves and neurons. This
damage can be caused by either an illness or an injury. There are a great number of
conditions which can affect a person. Some conditions are present from birth, while
others can be acquired through illness or injury. Neurological conditions can
therefore affect anyone from any background and at any stage in life.
Some people will have their condition throughout their entire lifetime and others will
acquire the condition later on in life. Some conditions are degenerative, meaning
they get worse; other conditions stay the same or come and go, such as migraines.
Some neurological conditions are life threatening, while others cause disability,
including mental and physical impairments. All neurological conditions have the
potential to threaten a person’s quality of life and his or her ability to live
independently. People who have a neurological condition have to learn to live life as
fully as possible and may need support to do so.
This course will look at some of the more common neurological conditions that you
will come across as a carer, and will provide you with the information you need to
support these people.
In order to understand neurological conditions, it is important to have a basic
understanding of how the brain and nervous system works when it functions
normally.
Overview of the Central Nervous System (CNS)
The central nervous system is made up of the
brain, the spinal cord and nerves.
The brain controls everything our body does. It
can be compared to a computer, as it makes
sense of all the messages it receives from the
spinal cord and the neurons. Our brain controls
what we think, what we say, our emotions,
memories, sensations, and body movements. It
also allows us to interpret messages given by
other organs in the body, such as the desire to
use the toilet. The brain therefore plays a part in
everything we do, including interpreting images,
sounds and smells.
The brain is made up of 100 billion nerve cells
called neurons. Neurons are connected to the rest
of the body via the spinal cord. The spinal cord
hosts a network of nerves which lead from there to
other parts of the body. The spinal cord can
therefore be seen as part of the brain.
How the Central Nervous System Works
The central nervous system can be seen as a hierarchy, with the brain sitting at the
top. A nerve in the body will have to send a message to the spinal cord, which then
sends the message up to the brain. The brain then processes the message and
interprets what to do with the information, sending instructions to the muscles. For
example, when the bladder is full, the bladder’s nerves will tell the spinal cord, which
then relays the message to the brain. The brain then decides if it is time to visit the
toilet, and sends instructions for the bladder muscles to release.
A Reference Guide to the Brain
The brain is made up of many parts, and it is important to understand the basic
functions of the important parts. Damage in any area, even damage which is very
small, can result in loss of function. When someone experiences brain damage, he
or she also experiences impairment of skills. Knowing what part of the brain is
damaged therefore tells us what function that part of the brain performs.
Scientists have used this knowledge to map the brain to psychological and physical
functions. The brain is divided into three main parts: the stem, the cerebellum, and
the cerebrum (also called the cerebral cortex).
1. The brain stem is located at the top of the spinal cord, and it is this which
keeps us alive. The stem is further divided into three sections: the mid brain
allows the left and right hemispheres to communicate; the pons is a like a
junction for all of the nerves; and the medulla controls our heart and lungs
(cardiac and respiratory functions).
2. The cerebellum is at the back of the skull and allows us to balance and coordinate movement.
3. The cerebrum (or cerebral cortex) contains the two hemispheres, which are
further divided into 4 lobes. The role of the cerebrum will now be looked at in
more detail, as this part of the brain performs the very specific functions that
make us individual.
A Tale of Two Halves
The cerebrum is divided into two halves
which are joined in the middle. Both of
these halves are referred to as
“hemispheres”. The left hemisphere
controls the right-hand side of the body, and
the right hemisphere controls the left-hand
side of the body. This means that if a
person has damage to the left side of the
brain, he will have difficulties using the right
hand side of his body. Similarly, one side of
the brain is “dominant”. For most of us, this
is the left-hand side, and we are therefore
right-handed. Left-handed people are rightbrain dominant.
Each hemisphere of the cerebrum is divided into four lobes, called the frontal,
parietal, temporal, and occipital lobes. Each of these lobes has its own physical
and mental functions to perform, and brain damage in these regions would affect a
person’s ability to perform those functions.
The Frontal Lobes
As its name suggests, the frontal lobe is located at the front of each hemisphere of
the brain. The frontal lobes are vital for each of our personalities, as emotion,
problem solving, planning, reasoning, and control of movement is located there. The
main job of the frontal lobes is to think things through and to decide how to use the
information that the rest of the brain is taking in. The frontal lobes are important in
performing several tasks:
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Problem solving: High-level and detailed thinking is possible because of the
frontal lobes, which allow us to reason, make plans, make choices, plan
courses of action, think through alternatives, and make judgments. Without
the frontal lobes, it is possible to be intelligent, but the brain would not be able
to process intelligent thinking.
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Social interaction: The frontal lobes allow us to access our memories and
also to interact with others appropriately. The frontal lobes help us to interpret
social cues, letting us know when to hold back in social situations and helping
us to differentiate between what is socially acceptable and what is not. They
allow us to understand empathetic behaviour, to know what other people are
thinking, and to interpret their emotions.
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Emotional control: The left frontal lobe is used to control emotion. If this part
of the brain is damaged, the person will display exaggerated emotional
responses without inhibition. She will also have difficulty interpreting facial
expression.
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Movement: Muscle control is located in another part of the brain, but the
frontal lobes allow voluntary control of movement, such as the ability to walk,
run, and throw or catch a ball.
The Temporal Lobes
The temporal lobes are located near the ears, and they are important for processing
sensory information. The main functions are thought to be making sense of what we
see and hear and also directing language.
As temporal lobes process sensory information, they play an important part in
memory retrieval. If you smell a perfume that reminds you of your first date, this
memory is triggered by the scent, which is processed in the temporal lobe.
The Parietal Lobes
The parietal lobes are located in the upper part of the back brain. They are involved
in the appreciation of sensation. It is the parietal lobes which make us identify if we
are hot or cold, or help us to decide if food smells good, has a nice texture, or tastes
foul. The parietal lobes also play a part in our spatial awareness, allowing us to
realize what is part of our body and what is not. For instance, they help us to gauge
if there is enough space to park a car, if the road is long, or if a cat will fit through a
particular gap. Reading and mathematical ability have also been mapped to this
region of the brain.
The Occipital Lobes
The occipital lobes are involved in vision. Namely, they deal with the information sent by the
eyes. As you read this page, your occipital lobes are working by processing the sensory
input from your eyes and linking it to your memories. For example, you can remember what
different letters and words are, and correctly interpret their meaning. The occipital lobes
therefore allow us to make inferences. For instance, we can always recognize a cat as a
cat: whether this is a real animal, a photograph, or a basic line
Module 1 – The Brain and the Central Nervous System (CNS)
Activity 1
Name the 3 components of the central nervous system.
1.
2.
3.
Activity 2
Explain the relationship between parts of the brain and behaviour.
Activity 3
What functions do the following brain parts have?
a.
b.
c.
d.
a.
b.
c.
d.
cerebellum
cerebral cortex
pons
medulla
Activity 4
Outline the main responsibility of the frontal lobes and name four important tasks that
they carry out.
Activity 5
Outline the main responsibility of the parietal lobes and name four important tasks
that they carry out.
Activity 6
Outline the main responsibility of the occipital lobes and name the main tasks that
they carry out.
Activity 7
Explain what is meant by “cortical blindness”.